Pace of research 'simply dazzling,' with four soon-to-be approved agents adding to treatment options

Photograph by: File photo
, Vancouver Sun

We don't know what cancer killed Jack Layton, but we do know he had prostate cancer and that it is common for men with prostate cancer to develop secondary cancers -- often more aggressive cancers which could be the ones that defeat them. For men, this is sobering news since prostate cancer is the most common form of the disease among men.

About 25,000 new cases of the disease surface in Canada each year. In BC, physicians diagnose approximately 3,000 new cases each year.

While most men survive the slow progressing disease, about 500 BC men die from it every year.

Others are aggressively treated for a cancer that will never bother them, raising questions about the value of regular PSA tests.

The good news is that research has been going on at a furious pace in world labs and in Vancouver's own internationally renowned Prostate Centre and it is starting to make its way into the clinic.

Dr. Kim Chi, an oncologist specializing in prostate cancer, says after years in the wilderness, four new agents targeting prostate cancer are in the final stages of approval.

"All of a sudden we have four new ways of attacking the cancer," says Chi, adding that before that, there was only one chemotherapy drug for late stage prostate cancer. Before that came on the scene 10 years ago, hormone therapy and castration surgery were the only treatments available.

"It's really exciting times and it's a testament to how much research has evolved," says Chi. "All these things you have been hearing about from scientific and lab studies are all coming to fruition in the clinic."

Dr. Martin Gleave, executive director of the Vancouver Prostate Centre, calls the current rate of discovery and development of new treatments "simply dazzling." He compares it to the '70s and early '80s when computer technology took off.

"Significant progress is being made now and we will look back in 20 years time and recognize this time as a magical coming of age period," he said.

The conundrum researchers are starting to wrestle to the ground is how to block the ability of cancer cells to evolve and survive the death blows medicine inflicts on them, says Gleave.

"Testosterone in the main driver of progression of prostate cancer," he explains, adding that treatment has always been to suppress the production of the male hormone. But when they do that, the cancer cells start producing testosterone themselves. " It shows you what little buggers they are," he says.

So research focuses on developing a cocktail of death blows that will keep medicine ahead of the cancer's survival tricks.

Comparing the research approach to a game of baseball, Gleave says researchers are advancing the runners with a series of base hits.

"It is unlikely we will hit home runs," he says. "We may, but right now we are moving the field along with a series of base hits and that is still the most predictable way to win the game."

Recently up to bat was a new drug just approved in Canada a few weeks ago called Abiraterone, which showed excellent results. Abiraterone is a pill that blocks the cancer cell's ability to produce testosterone and it has very few side effects.

"We were testing it for several years on people with no other treatment options," said Chi, adding the average survival for the subjects was less than one year.

"Guys in wheelchairs were getting up and walking after one to two weeks of treatment," he said adding that it improved survival by about 35 per cent. People also had less pain and less progression of cancer," says Chi.

The drug was tested on men at the end stages of the disease, but Chi expects it may eventually become first line treatment, even before surgery and radiation.

Another new player is a drug called Denosumab, which is now on the market. It prevents the cancer cells from harming the bones. When prostate cancer metastasizes, it usually goes to the bone. Denosumab is an anti-body that shuts down the cancer-activated cells that can destroy the bone. Patients can easily self-administer it and while it doesn't prolong life, it does a lot to improve quality of life, says Chi.

Then there is a new chemotherapy drug for patients who have become resistant to current chemotherapy regimes, and a new vaccine-type treatment that has been approved in the U.S., but not in Canada. The vaccine prolongs survival for about four months, but it doesn't relieve symptoms and it's expensive. It is questionable if patients will want to prolong their suffering while depleting their bank accounts, said Chi.

These four agents have all shown promise to varying degrees, but five more treatments are on the horizon, says Gleave.

One that is highly anticipated is a drug called OGX 011, which was developed by a team led by Gleave. In phase two trials it was found to restore the efficacy of chemotherapy in patients who had become resistant to the drugs and prolonged the lives of end-stage patients for an average of seven months. It is now in randomized phase three trials. Gleave says the data are very promising and will be out within two years.

The Prostate Centre researchers are also trying to figure out how to tell the difference between a prostate cancer that will kill and one that stays quiet in the body, not bothering it, says Chi.

By isolating and analyzing what they call circulating tumour cells, which are found in the blood stream and can be removed with a simple blood sample, researchers hope to figure out what drives a particular cancer. Once they know that, they can develop treatments that specifically target those drivers. It may also help them determine which cancers are less harmful than the treatment.

"This is in baby steps right now, but it is part of the future," he says.

Layton's demise was unfortunate and even tragic, but as he said himself, it's not a reason for those with the disease to lose hope. Instead, men can take comfort knowing that an explosion of discoveries in the field is greatly enhancing chances of survival.

"Fifteen years ago if you had end stage hormone resistant prostate cancer your overall survival rate was 12-14 months," says Gleave. "Now with the addition of these new medications, survival is exceeding 25 months and will continue to grow over the next five years."

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